Imports System

Public Module Module1

    Public Sub Main()

        dim mark as integer = console.readline()

        select case mark

    case > 80

            console.writeline("your mark is A")

    case > 70

            console.writeline("your mark is B")

        case > 60 

            console.writeline("your mark is C")

        case > 50

            console.writeline("your mark is D")

        end select

    End Sub

End Module